Attaching dissimilar surfaces of planar textiles or textile elements using adhesives is affected by the structural dissimilarities among the surfaces. The density or porosity or affinity for adhesive among the surfaces can vary, and certain surfaces may benefit more from the propagation of adhesive. For example, textile layers are generally porous and require large amounts of adhesives to achieve secure bonding among the layers as the adhesives tend to follow the direction of lowest resistance and propagate more into the more porous layers and less into the less porous layers. Therefore, attaching porous textile layers to less porous layers is difficult. Bulky felts are generally porous, and fabrics are less porous. Attachment of a dense fabric to a bulky felt without a large portion of the adhesive propagating into the bulky felt is difficult.
Incompatibility between layers also occurs when one surface is less receptive to adhesion than the opposing surface, for example, the attachment of two textile surfaces using a polymeric adhesive more compatible with the fibers on one surface than the fibers of the other surface. The less receptive or compatible surface requires propagation of a higher percentage of the adhesive. Layers that are treated to repel fluids such as water require a higher degree of adhesive penetration to achieve a satisfactory bond.
When elements on one surface are relatively loose, these loose elements need to be secured by the propagation of adhesive upon the application or pressure as opposed to the propagation away from the loose elements and toward the adjacent textile surface. One example of such a need is the attachment a tufted fabric to a secondary textile backing with sufficient tuft security or “tuft-bind”. This is conventionally achieved by simultaneously attaching the “back-laps” of the tufted yarns to the primary and secondary backings. Copious quantities of low-viscosity adhesives such as latex solutions or heavy layers of low-melting, low-viscosity polymers are typically used to reach, to contain and to secure the back-laps. As a second example, secondary under-layers attached to face fabrics that provide cushioning, for example, felts and foam layers, are porous and are difficult to secure as excessive propagation of adhesive into these cushioning under-layers occurs.
Adhesive layers contained within a textile product as it is formed also take the path of least resistance when activated. This path of least resistance tends to be undesirable for achieving the desired bonding and properties in the textile product. For example, a stitch-bonded fabric is formed with a low-melting substrate that is activated with heat and pressure. The desire is to have the activated adhesive propagate to one of the surfaces, e.g., the “technical front” or the “technical back”, to increase abrasion resistance while keeping the opposite surface free of adhesive to maintain a soft textile feel. In another example concerning needle-punched fabrics such as felts, a low-melting adhesive layer is encapsulated between two fibrous layers. Creating a dense sealed and wear-resistant composite surface requires directing this adhesive to one of the two fibrous layers and away from the other fibrous layer.
In addition to directing adhesive into a desired layer, it is also desirable to direct adhesive in the planar direction between layers so that, while using a uniform adhesive sheet, textile layers can be preferentially joined at separated open spots or lines or areas arranged in different patterns for the sake of softness, or permeability, or stress control, special design effects, or other similar needs.